We use the first Gaia data release , combined with RAVE and APOGEE spectroscopic surveys , to investigate the origin of halo stars within \lesssim 3 kpc from the Sun .
We identify halo stars kinematically , as moving with a relative speed of at least 220 km/s with respect to the local standard of rest .
These stars are in general more metal-poor than the disk , but surprisingly , half of our halo sample is comprised of stars with [ Fe / H ] > -1 .
The orbital directions of these metal-rich halo stars are preferentially aligned with the disk rotation , in sharp contrast with the isotropic orbital distribution of the more metal-poor halo stars .
We find similar properties in the Latte cosmological zoom-in simulation of a Milky Way-like galaxy from the FIRE project .
In Latte , metal-rich halo stars formed primarily inside of the solar circle , while lower-metallicity halo stars preferentially formed at larger distances ( extending beyond the virial radius ) .
This suggests that metal-rich halo stars in the Solar neighborhood in fact formed in-situ within the Galactic disk rather than having been accreted from satellite systems .
These stars , currently on halo-like orbits , therefore have likely undergone substantial radial migration/heating .